In the microelectronics industry, there are Known-Good-Die (KGD) chips, which are die (chips) that have been tested and burned-in, and are known to be good prior to sale. Moreover, it is necessary that chips used to populate a multi-chip module (MCM) be (KGD) chips prior to being placed on the MCM, so that it is not necessary to reflow the module excessive times to replace die (chips) that may be defective.
One method of producing KGD chips is to test the die on an Alumina Based Ceramic carrier. The Alumina Based Ceramic carrier can be a standard single-chip substrate. If the tested die is found to be good, the die is removed and put in a Known-Good-Die bank. The Alumina Based Ceramic, standard single-chip substrate is then cleaned and re-used.
Conventional methods such as the flip-chip attach are common in the electronics industry. However, problems arise when a chip is temporarily mounted on a carrier with chip solder balls to provide sufficient electrical connectivity to facilitate test and burn-in at elevated temperatures. One problem is that it is difficult to then remove the chip from the Temporary Chip Attach (TCA) carrier (substrate) without damage to the chip solder balls or the carrier. Glass ceramic based carriers are much more fragile then alumina based Ceramic based carriers and it is even more difficult for them to withstand the removal process.
In order to serve as a Temporary Chip Attach (TCA) substrate, a standard substrate is put through a special process flow which reduces the solder area, thus minimizing the joint strength, and allowing for easy removal of the die when the testing is complete.
The process to convert a standard substrate to a TCA substrate is expensive, complicated, and not well defined or controlled. First, only alumina based substrates can be readily used. If the original application was for use on a glass ceramic substrate, then the testing results for the die on an alumina based substrate may not match the die performance when placed on the glass ceramic substrate due to differences arising from substrate contributions. The inaccuracies in the testing results can cause improper sorting of the tested die. Special mask and process steps need to be added to the standard substrate during manufacturing flow to convert it to a TCA substrate. This special processing and design work is expensive and time consuming. Therefore, what is needed is an improved technique for performing Temporary Chip Attach.